Solid-state image pickup device, image pickup system using solid-state image pickup device, and method of manufacturing solid-state image pickup device

ABSTRACT

In a solid-state image pickup device including a pixel that includes a photoelectric conversion portion, a carrier holding portion, and a plurality of transistors, the solid-state image pickup device further includes a first insulating film disposed over the photoelectric conversion portion, the carrier holding portion, and the plurality of transistors, a conductor disposed in an opening of the first insulating film and positioned to be connected to a source or a drain of one or more of the plurality of transistors, and a light shielding film disposed in an opening or a recess of the first insulating film and positioned above the carrier holding portion.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.13/473,455, filed May 16, 2012, which claims priority from JapanesePatent Application No. 2011-119257 filed May 27, 2011, which are herebyincorporated by reference herein in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One disclosed aspect of the embodiments relates to a solid-state imagepickup device, an image pickup system using the solid-state image pickupdevice, and a method of manufacturing the solid-state image pickupdevice.

2. Description of the Related Art

In an active-pixel type solid-state image pickup device represented by aComplementary Metal Oxide Semiconductor (CMOS) image sensor, it isproposed to a device having a global electronic shutter function orincluding focus detection pixels.

The global electronic shutter function is a function of starting andending accumulation of photo-carriers (photo-charges) in a plurality ofpixels, which are arrayed in a matrix pattern, simultaneously for allthe pixels. The solid-state image pickup device having the globalelectronic shutter function includes, in each pixel, a photoelectricconversion portion and a carrier holding portion configured to holdcarriers, which are generated by photoelectric conversion, for a certaintime. The carrier holding portion in the solid-state image pickup devicehaving the global electronic shutter function holds the carriers for aperiod from the end of the accumulation of the photo-carriers to read ofthe accumulated photo-carriers. There is a possibility that if, duringsuch a period, carriers generated other than the photoelectricconversion portion are mixed into the carrier holding portion, the mixedcarriers may generate a noise signal, thus causing degradation of imagequality. Japanese Patent Laid-Open No. 2008-004692 discloses a structurewhere each pixel includes a photoelectric conversion portion and acarrier holding portion, and a light shielding film is disposed on thecarrier holding portion.

Japanese Patent Laid-Open No. 2009-105358 discloses a solid-state imagepickup device including focus detection pixels, in which a lightshielding film having a slit is disposed in the focus detection pixel.Japanese Patent Laid-Open No. 2008-004692 mentions the light shieldingfilm, but detailed discussion is not made regarding the light shieldingfilm. Depending on the arrangement of the light shielding film, obliquelight may become apt to enter the carrier holding portion, and carriersgenerated by the oblique light may be mixed into the carriers held inthe carrier holding portion.

The solid-state image pickup device disclosed in Japanese PatentLaid-Open No. 2009-105358 also accompanies with a similar problem tothat described above because detailed discussion is not made regardingthe light shielding film including the slit.

SUMMARY OF THE INVENTION

One disclosed aspect of the embodiments provides a solid-state imagepickup device including a light shielding film that has high lightshielding performance, and a method of manufacturing solid-state imagepickup device.

According to one embodiment, there is provided a solid-state imagepickup device including a pixel, which includes a photoelectricconversion portion, a carrier holding portion configured to holdcarriers generated in the photoelectric conversion portion, and aplurality of transistors configured to output a signal based on thecarriers in the carrier holding portion; a first insulating filmdisposed over the photoelectric conversion portion, the carrier holdingportion, and the plurality of transistors; and a conductor disposed inan opening of the first insulating film and positioned to be connectedto a source or a drain of one or more of the plurality of transistors,wherein the solid-state image pickup device further includes a lightshielding film disposed in an opening or a recess of the firstinsulating film and positioned above the carrier holding portion.

According to another embodiment, there is provided a method ofmanufacturing a solid-state image pickup device including aphotoelectric conversion portion, a carrier holding portion configuredto hold carriers generated in the photoelectric conversion portion, anda plurality of transistors including a transistor to output a signalbased on the carriers in the carrier holding portion, the methodincluding the operations of forming a first insulating film that coversthe photoelectric conversion portion, the carrier holding portion, andthe plurality of transistors, removing a part of the first insulatingfilm above the carrier holding portion, and forming a light shieldingfilm in a portion that is formed by removing the part of the firstinsulating film.

Further features of the disclosure will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic sectional view of a solid-state image pickupdevice according to a first embodiment.

FIG. 1B is a schematic sectional view of the solid-state image pickupdevice according to the first embodiment.

FIG. 2A is a schematic sectional view illustrating a method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 2B is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 2C is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 2D is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 2E is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 2F is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 2G is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to the firstembodiment.

FIG. 3A is a schematic sectional view to explain the solid-state imagepickup device according to the first embodiment.

FIG. 3B is a schematic sectional view to explain the solid-state imagepickup device according to the first embodiment.

FIG. 4A is a schematic sectional view of a solid-state image pickupdevice according to a second embodiment.

FIG. 4B is a schematic sectional view of the solid-state image pickupdevice according to the second embodiment.

FIG. 5A is a schematic sectional view illustrating a method ofmanufacturing the solid-state image pickup device according to thesecond embodiment.

FIG. 5B is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to thesecond embodiment.

FIG. 5C is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to thesecond embodiment.

FIG. 5D is a schematic sectional view illustrating the method ofmanufacturing the solid-state image pickup device according to thesecond embodiment.

FIG. 6A is a schematic sectional view illustrating a method ofmanufacturing a solid-state image pickup device according to a thirdembodiment.

FIG. 6B is a schematic sectional view illustrating the method ofmanufacturing a solid-state image pickup device according to the thirdembodiment.

FIG. 6C is a schematic sectional view illustrating the method ofmanufacturing a solid-state image pickup device according to the thirdembodiment.

FIG. 6D is a schematic sectional view illustrating the method ofmanufacturing a solid-state image pickup device according to the thirdembodiment.

FIG. 6E is a schematic sectional view illustrating the method ofmanufacturing a solid-state image pickup device according to the thirdembodiment.

FIG. 6F is a schematic sectional view illustrating the method ofmanufacturing a solid-state image pickup device according to the thirdembodiment.

FIG. 7A is a schematic sectional view of a solid-state image pickupdevice according to a fourth embodiment.

FIG. 7B is a schematic plan view of the solid-state image pickup deviceaccording to the fourth embodiment.

FIG. 8 illustrates an example of a pixel circuit in a solid-state imagepickup device.

DESCRIPTION OF THE EMBODIMENTS

A solid-state image pickup device according to an embodiment includes aphotoelectric conversion portion, a plurality of transistors, aninsulating film disposed over the photoelectric conversion portion andthe plurality of transistors, and a conductor disposed in an opening ofthe insulating film and positioned to be connected to a source or adrain of one or more of the plurality of transistors. The solid-stateimage pickup device further includes a light shielding film disposed inthe insulating film in which the conductor is disposed. The lightshielding film is disposed in the insulating film at a position above astructure that is to be shielded from light, e.g., above a carrierholding portion in a solid-state image pickup device having the globalelectronic shutter function or above a photoelectric conversion portionin a solid-state image pickup device including focus detection pixels.Such an arrangement contributes to increasing light shieldingperformance of the light shielding film.

In the following description, a direction toward the inside of asemiconductor substrate from a surface of the semiconductor substrate isdefined as a downward direction, and a direction opposed to thatdirection is defined as an upward direction. Also, the followingembodiments are described in connection with the case that signalcarriers (charge carriers) are electrons.

The embodiments will be described in detail below with reference to thedrawings.

First Embodiment

FIG. 8 is a circuit diagram for four pixels in a solid-state imagepickup device according to a first embodiment. In FIG. 8, pixels 800 arearrayed in two rows and two columns. Each of the pixels 800 includes aphotoelectric conversion portion 801, a carrier holding portion 802, afirst transfer transistor 804, a second transfer transistor 805, anamplification transistor 806, a selection transistor 807, and a resettransistor 808. The pixel 800 further includes a third transfertransistor 809 for overflow drain (hereinafter abbreviated to “OFD”) todrain useless carriers. Reference numeral 803 in the pixel 800 denotes anode including a floating diffusion portion (hereinafter referred to asan “FD portion”). A power line 810 and a power line 811 are each awiring to supply a predetermined voltage. The power line 810 isconnected to a main electrode region of the OFD transistor 809. Thepower line 811 is connected to respective main electrode regions of thereset transistor 808 and the selection transistor 807. RES, TX1, TX2,SEL and TX3 represent control lines for supplying pulses to respectivegate electrodes of the corresponding transistors. The pulses aresupplied from a vertical scanning circuit (not illustrated). In moredetail, RES represents a control line for supplying a pulse to the gateelectrode of the reset transistor 808, TX1 represents a control line forsupplying a pulse to the gate electrode of the first transfer transistor804, and TX2 represents a control line for supplying a pulse to the gateelectrode of the second transfer transistor 805. SEL represents acontrol line for supplying a pulse to the gate electrode of theselection transistor 807, and TX3 represents a control line forsupplying a pulse to the gate electrode of the third transfer transistor809. OUT represents a signal line. Characters n and m in FIG. 8 are eacha natural number. Thus, n represents a certain row, and n+1 represents arow adjacent to the certain row n. Further, m represents a certaincolumn, and m+1 represents a column adjacent to the certain row m. Thesignal output from the signal line OUT is held in a read circuit (notillustrated) and is output to the outside of the solid-state imagepickup device after being subjected to processing such as amplificationand addition. On that occasion, control signals for controlling theprocessing, such as the signal addition, and the signal outputting tothe outside may be supplied from a horizontal scanning circuit (notillustrated). A constant-current source constituting a source followercircuit in combination with the amplification transistor may be disposedin the signal line OUT. In FIG. 8, the pixel 800 is a structureincluding one photoelectric conversion portion 801 and is a minimumrepetition unit in the structure of the solid-state image pickup device.It is to be noted that the pixel 800 is not limited to theabove-described structure. For example, one amplification transistor maybe shared by a plurality of pixels.

A global shutter operation in the pixel 800 of FIG. 8 is performed asfollows. After the lapse of a certain accumulation period, signalcarriers generated in the photoelectric conversion portion 801 aretransferred to the carrier holding portion 802 through the firsttransfer transistor 804. While the carrier holding portion 802 isholding the signal carriers for the certain accumulation period, theaccumulation of signal carriers is started again in the photoelectricconversion portion 801. The signal carriers in the carrier holdingportion 802 are transferred to the node 803, including the FD portion,through the second transfer transistor 805 and are output as a signalfrom the amplification transistor 806. In some cases, the signalcarriers in the photoelectric conversion portion 801 may be drainedthrough the third transfer transistor 809 so that the signal carriersgenerated in the photoelectric conversion portion 801 are not mixed intothe carrier holding portion 802 while the carrier holding portion 802 isholding the signal carriers. The reset transistor 808 sets the node 803,including the FD portion, to a predetermined potential (called a resetoperation) before the signal carriers are transferred thereto from thecarrier holding portion 802. A noise signal may be removed byoutputting, as the noise signal, the potential of the node 803 includingthe FD portion at that time to the signal line OUT through theamplification transistor 806, and by taking a differential between thenoise signal and a later-output signal on the basis of the signalcharges.

Regarding the solid-state image pickup device including the carrierholding portion which may perform the global shutter operation describedabove, FIG. 1A illustrates a light shielding arrangement for the carrierholding portion. FIG. 1A is a schematic sectional view illustrating thephotoelectric conversion portion 801, the carrier holding portion 802,and the floating diffusion portion (FD portion) 803 illustrated in FIG.8, as well as a light shielding film 116 arranged above the carrierholding portion 802. Although a structure above the light shielding film116 is omitted, a wiring structure, a protection film, a color filter,an in-layer lens, a microlens, etc. may be arranged as appropriate abovethe light shielding film 116. The same components in FIG. 1A as those inFIG. 8 are denoted by the same reference numerals and description ofthose components is omitted.

In FIG. 1A, a semiconductor substrate 101 is, e.g., a siliconsemiconductor substrate. The semiconductor substrate 101 has a surface100 and a P-type semiconductor region 102 formed therein. An elementisolation region 103 is disposed in the semiconductor substrate 101 andis formed by the STI (Shallow Trench Isolation) method. Thephotoelectric conversion portion 801 includes an N-type semiconductorregion 105 functioning as a carrier accumulation portion, and a P-typesemiconductor region 104 disposed on the N-type semiconductor region105. An N-type semiconductor region 106 constitutes the carrier holdingportion 802, and an N-type semiconductor region 107 constitutes thefloating diffusion portion (FD portion) 803. A gate electrode 108constituting the first transfer transistor 804 is disposed on a gateinsulating film 109 that is disposed on the surface 100 of thesemiconductor substrate 101. The gate electrode 108 is positionedbetween the N-type semiconductor region 105 and the N-type semiconductorregion 106. A gate electrode 110 constituting the second transfertransistor 805 is disposed on a gate insulating film 111 that isdisposed on the surface 100 of the semiconductor substrate 101, and itis positioned between the N-type semiconductor region 106 and the N-typesemiconductor region 107. An insulating film integral with the gateinsulating film 111 or an insulating film separate therefrom may bedisposed on the surface 100 in an area other than under the gateelectrode 110.

In FIG. 1A, an insulating film 112 (second insulating film) is disposedto cover the photoelectric conversion portion 801, the gate electrode108, the gate electrode 110, etc. Further, an insulating film 113 (firstinsulating film) is disposed on the insulating film 112. The insulatingfilm 113 is a silicon oxide film, for example, and it may function as aninterlayer insulating film. The insulating film 113 may also function asa planarizing film that planarizes unevenness caused by the presence ofthe gate electrodes, etc. The insulating film 112 is a silicon nitridefilm, for example, and it may function as a protection film for thesurface of the photoelectric conversion portion 801. Further, theinsulating film 112 has a higher refractive index than the insulatingfilm 113, and the insulating film 112 may function as an antireflectionfilm that reduces reflection at the surface of the photoelectricconversion portion 801. The insulating film 112 may be a layered filmmade up of a silicon nitride film, a silicon oxide film, a siliconoxynitride film, etc.

In FIG. 1A, a conductor 115 disposed in respective openings of theinsulating film 112 and the insulating film 113 may function as acontact plug. The conductor 115 is made of, e.g., tungsten. A metalwiring (not illustrated) is arranged on the conductor 115. An N-typesemiconductor region 114 is disposed to establish ohmic connectionbetween the conductor 115 serving as the contact plug and thesemiconductor region 107, and it has a higher impurity concentrationthan the semiconductor region 107. The light shielding film 116 isdisposed in the insulating film 113 to cover the N-type semiconductorregion 106 constituting the carrier holding portion 802. The lightshielding film 116 is made of, e.g., tungsten.

Thus, since the light shielding film 116 is disposed in the insulatingfilm 113 where the conductor 115 serving as the contact plug isdisposed, i.e., on the side closer to the surface 100 of thesemiconductor substrate 101 than the metal wiring, light may be blockedat a position closer to the N-type semiconductor region 106 constitutingthe carrier holding portion 802. It is hence possible to reduce mixingof light into the carrier holding portion 802 and to obtain higher lightshielding performance.

The light shielding film 116 is formed to extend from a position abovethe gate electrode 110 of the second transfer transistor 805 up to aposition above the photoelectric conversion portion 801 while coveringthe carrier holding portion 802 and the gate electrode 108 of the firsttransfer transistor 804. Such coverage relation of the light shieldingfilm 116 is similar in a direction perpendicular to the drawing sheet ofFIG. 1A as well. Thus, since light is blocked over a wider range thanthe carrier holding portion 802, it is possible to reduce mixing oflight into the carrier holding portion 802 and to obtain higher lightshielding performance.

A method of manufacturing the solid-state image pickup device accordingto the first embodiment will be described below with reference to FIGS.2A to 2G. The same components in FIGS. 2A to 2G as those in FIG. 1A aredenoted by the same reference numerals and description of thosecomponents is omitted.

First, in FIG. 2A, the P-type semiconductor region 102, the elementisolation region 103, the N-type semiconductor region 105, the P-typesemiconductor region 104, the N-type semiconductor region 106, and theN-type semiconductor region 107 are formed in the semiconductorsubstrate 101. The element isolation region 103 is formed by the STImethod, and the semiconductor regions are formed by photolithography andion implantation. Further, the gate electrode 108 and the gate electrode110 are formed by photolithography and etching by using polysilicon. Atthe same time, the gate insulating film 109 and the gate insulating film111 are also formed. Those components may be formed by using generalsemiconductor techniques, and detailed description of methods forforming them is omitted. Moreover, the order of operations of formingthose components is optionally selected.

Further, as illustrated in FIG. 2A, an insulating film 201 made of asilicon nitride film is formed by low-pressure CVD (LPCVD) to cover thesurface 100 of the semiconductor substrate 101 and the gate electrodes108 and 110. An insulating film 202 made of a silicon oxide film is thenformed over the insulating film 201. In this state, the insulating film201 has a surface following the unevenness corresponding to the gateelectrodes, etc., while the insulating film 202 planarizes theunevenness corresponding to the gate electrodes, etc. and has a flatsurface.

Next, as illustrated in FIG. 2B, a photoresist pattern 203 is formed onthe insulating film 202. The photoresist pattern 203 serves as a maskfor use in forming a contact hole 204 in the insulating film 202 and hasan opening to form the contact hole 204. Etching is then carried out onthe insulating films 202 and 201 with the photoresist pattern 203 usedas a mask, thereby removing respective parts of the insulating films 202and 201 and forming the contact hole 204 in the insulating films 202 and201. At that time, the insulating film 201 may function as an etchingstopper in the etching to form the contact hole.

After forming the contact hole 204, an N-type impurity is ion-implantedinto the contact hole 204 to form the N-type semiconductor region 114(FIG. 2C). Further, the photoresist pattern 203 is removed and aconductor film 204′ is formed (FIG. 2C). The conductor film 204′ is,e.g., a layered film of titanium nitride and tungsten.

Etching or CMP is performed on the conductor film 204′ to remove anextra portion of the conductor film 204′, whereby the conductor 115 isformed in the contact hole 204 (FIG. 2D).

Next, a photoresist pattern 205 is formed over the conductor 115 and theinsulating film 202 (FIG. 2E). The photoresist pattern 205 serves as amask for use in forming the light shielding film 116 in the insulatingfilm 202 and has an opening to form the light shielding film 116.Etching is then carried out on the insulating film 202 with thephotoresist pattern 205 used as a mask, thereby removing a part of theinsulating film 202 and forming, in the insulating film 202, a recess206 where the light shielding film 116 is to be formed. In this state, abottom surface the recess 206 is positioned above the gate electrodes108 and 110.

Further, the photoresist pattern 205 is removed and a conductor film 207is formed (FIG. 2F). The conductor film 207 is, e.g., a layered film oftitanium nitride and tungsten. Etching or CMP is performed on theconductor film 207 to remove an extra portion of the conductor film 207,whereby the light shielding film 116 is formed in the recess 206 that isa portion formed by removing a part of the insulating film 113. Here,the insulating film 202 becomes the insulating film 113 (FIG. 2G). Insuch a manner, the light shielding film 116 may be formed in theinsulating film 113 in which the conductor 115 serving as the contactplug is disposed.

FIG. 1B illustrates a modification of the solid-state image pickupdevice according to the first embodiment. The same components in FIG. 1Bas those in FIG. 1A are denoted by the same reference numerals anddescription of those components is omitted. FIG. 1B differs from FIG. 1Ain the arrangement of the light shielding film. The light shielding film116 in FIG. 1A is formed to extend from a position above the gateelectrode 110 of the second transfer transistor 805 up to a positionabove the photoelectric conversion portion 801 while covering thecarrier holding portion 802 and the gate electrode 108 of the firsttransfer transistor 804. On the other hand, a light shielding film 117in FIG. 1B is formed to extend from a position above the gate electrode110 of the second transfer transistor 805 up to a position above thegate electrode 108 of the first transfer transistor 804 while coveringthe carrier holding portion 802. In other words, the light shieldingfilm disposed in the insulating film 113 is positioned at least abovethe N-type semiconductor region 106 constituting the carrier holdingportion 802. With such an arrangement, since the light shielding film isdisposed near the carrier holding portion 802, mixing of light into thecarrier holding portion 802 may be reduced.

A wiring structure of the solid-state image pickup device according tothe first embodiment will be described below with reference to FIGS. 3Aand 3B. FIGS. 3A and 3B are each a schematic sectional view of thesolid-state image pickup device, the view corresponding to FIG. 1A. Thesame components in FIGS. 3A and 3B as those in FIG. 1A are denoted bythe same reference numerals and description of those components isomitted.

In FIG. 3A, the wiring structure is disposed above the insulating film113, the light shielding film 116, and the conductor 115 illustrated inFIG. 1A. The wiring structure is made up of, e.g., an insulating film301, an insulating film 302, a first wiring layer 303, a via layer 304,and a second wiring layer 305. The first wiring layer 303 is disposed inthe insulating film 301, and it includes a wiring 303 a and a wiring 303b. The via layer 304 is disposed in the insulating film 301 and includesa via 304 a and a via 304 b. The second wiring layer 305 is disposed inthe insulating film 302, and it includes a wiring 305 a and a wiring 305b. Here, each wiring is a metal wiring made of an alloy containingaluminum as a main ingredient. As an alternative, the metal wiring maybe a wiring made of an alloy containing aluminum and copper as mainingredients.

Above the light shielding film 116, the wiring 303 a, the via 304 a, andthe wiring 305 a are disposed in that order as viewed in the upwarddirection from the light shielding film 116 and are electricallyconnected to each other. Above the conductor 115, the wiring 303 b, thevia 304 b, and the wiring 305 b are disposed in that order as viewed inthe upward direction from the conductor 115 and are electricallyconnected to each other. Though not illustrated in the circuit of FIG.8, a voltage may be supplied to the light shielding film 116. Thesupplied voltage is, e.g., a ground voltage, a power source voltage, anda driving voltage in match with the carrier transfer operation.

FIG. 3B illustrates a modification of the wiring structure in FIG. 3A.Description of the same components in FIG. 3B as those in FIG. 3A isomitted. In FIG. 3B, as in FIG. 3A, the wiring structure is disposedabove the insulating film 113, the light shielding film 116, and theconductor 115 illustrated in FIG. 1A. The wiring structure is made upof, e.g., an insulating film 306, an insulating film 307, a first wiringlayer 309, and a via layer 308. The via layer 308 is disposed in theinsulating film 306, and it includes a via 308 a and a via 308 b. Thefirst wiring layer 309 is disposed in the insulating film 307, and itincludes a wiring 309 a and a wiring 309 b. Above the light shieldingfilm 116, the via 308 a and the wiring 309 a are disposed in that orderas viewed in the upward direction from the light shielding film 116 andare electrically connected to each other. Above the conductor 115, thevia 308 b and the wiring 309 b are disposed in that order as viewed inthe upward direction from the conductor 115 and are electricallyconnected to each other. The conductor 115 and the via 308 b constitutesa stack contact structure in which they are directly connected to eachother. In this modification, a voltage may be supplied to the lightshielding film 116 as in FIG. 3A.

Thus, since the light shielding film 116 is disposed in the insulatingfilm 113 where the conductor 115 serving as the contact plug isarranged, light may be blocked at a position close to the N-typesemiconductor region 106 constituting the carrier holding portion 802.It is hence possible to reduce mixing of light into the carrier holdingportion 802 and to obtain higher light shielding performance.

Second Embodiment

A solid-state image pickup device according to a second embodiment willbe described below with reference to FIGS. 4A, 4B and 5A to 5D. FIG. 4Ais a schematic sectional view of the solid-state image pickup device,the view corresponding to FIG. 1A. The same components in FIG. 4A asthose in FIG. 1A are denoted by the same reference numerals anddescription of those components is omitted.

FIG. 4A differs from FIG. 1A in the arrangement of the light shieldingfilm. While the light shielding film 116 in FIG. 1A is disposed in therecess formed in the insulating film 113, a light shielding film 401 inFIG. 4A is disposed in an opening, instead of the recess, formed in theinsulating film 113. The light shielding film 401 is stacked on theN-type semiconductor region 106 constituting the carrier holding portion802 with the insulating film 112 interposed therebetween such that thelight shielding film 401 fills a portion between the gate electrode 110and the gate electrode 108. Such an arrangement may further increase thelight shielding performance for the carrier holding portion 802.

Further, in FIG. 4A, the light shielding film 401 is arranged to extendfrom a position above the gate electrode 110 up to a position above thephotoelectric conversion portion 801. Such an arrangement may reduceincoming of light into the N-type semiconductor region 106 from thephotoelectric conversion portion 801, i.e., from the side of the gateelectrode 108 closer the N-type semiconductor region 105. Moreover,since in the photoelectric conversion portion 801 the light shieldingfilm 401 is disposed on the surface 100 of the semiconductor substrate101 with the insulating film 112 interposed therebetween, incoming oflight through an edge of the gate electrode 108 may also be suppressed.

Since the range where the light shielding film 401 is disposed isterminated at the position above the gate electrode 110, a sufficientdistance may be held relative to the conductor 115 disposed in thesemiconductor region 107. Such an arrangement may suppressshort-circuiting between the conductor 115 and the light shielding film401.

Further, the light shielding film 401 has a tapered shape such that alateral surface 402 of the light shielding film 401 is inclined relativeto the surface 100 of the semiconductor substrate 101. In more detail,the lateral surface 402 of the light shielding film 401 extends towardthe surface 100 of the semiconductor substrate 101 at a certain anglerelative to a direction perpendicular to the surface 100 of thesemiconductor substrate 101. Such a tapered shape is beneficial in that,even when incident light is reflected at the light receiving surface ofthe photoelectric conversion portion 801, the reflected light may bemade incident on the photoelectric conversion portion 801 because thereflected light impinges against the lateral surface 402 of the lightshielding film 401.

A method of manufacturing the solid-state image pickup device accordingto the second embodiment will be described below with reference to FIGS.5A to 5D. The same components in FIGS. 5A to 5D as those in FIG. 4A aredenoted by the same reference numerals and description of thosecomponents is omitted. Description of similar manufacturing operationsto those in the first embodiment (FIGS. 2A to 2G) is also omitted.

First, in FIG. 5A, the element isolation region 103, the varioussemiconductor regions, and the gate electrodes are formed in thesemiconductor substrate 101 as in FIG. 2A. Those components may beformed by using general semiconductor techniques, and detaileddescription of methods for forming them is omitted. Further, as in FIG.2A, an insulating film 501 made of a silicon nitride film is formed bylow-pressure CVD (LPCVD) to cover the surface 100 of the semiconductorsubstrate 101 and the gate electrodes 108 and 110. An insulating film502 made of a silicon oxide film is then formed over the insulating film501. In this state, the insulating film 501 has a surface following theunevenness corresponding to the gate electrodes, etc., while theinsulating film 502 planarizes the unevenness corresponding to the gateelectrodes, etc. and has a flat surface.

Next, as illustrated in FIG. 5B, a photoresist pattern 503 is formed onthe insulating film 502. The photoresist pattern 503 serves as a maskfor use in forming a contact hole 504 and a light shielding film in theinsulating film 502. Thus, the photoresist pattern 503 has an opening toform the contact hole 504 and an opening to form the light shieldingfilm. Etching is then carried out on the insulating film 502 with thephotoresist pattern 503 used as a mask, thereby removing a part of theinsulating film 502 and forming the contact hole 504 and an opening 505for the light shielding film in the insulating film 502. At that time,the insulating film 501 may function as an etching stopper in theabove-described etching.

After forming the contact hole 504 and the opening 505, the photoresistpattern 503 is removed. A new photoresist pattern 506 is then formed.The new photoresist pattern 506 has an opening where the contact hole504 is exposed, and it covers the other region than the contact hole504. Etching is carried out with the photoresist pattern 506 used as amask, thereby removing a part of the exposed insulating film 501. Then,an N-type impurity is ion-implanted into the contact hole 504 to formthe N-type semiconductor region 114 (FIG. 5C).

After removing the photoresist pattern 506, a conductor film 507 isformed (FIG. 5D). The conductor film 507 is, e.g., a layered film oftitanium nitride and tungsten. Etching or CMP is performed on theconductor film 507 to remove an extra portion of the conductor film 507.Thus, the conductor 115 is formed in the contact hole and the lightshielding film 401 is formed in the opening that is a portion formed byremoving a part of the insulating film 502, whereby the structure ofFIG. 4A is obtained. Here, the insulating film 501 becomes theinsulating film 112, and the insulating film 502 becomes the insulatingfilm 113.

In such a manner, the light shielding film 401 may be formed in theinsulating film 113 in which the conductor 115 serving as the contactplug is disposed. Further, the light shielding film 401 may be formed inthe same operation as that for forming the conductor 115 serving as thecontact plug. More specifically, the operations of forming the contacthole and the opening, forming the conductor film, and removing the extraportion of the conductor film may be performed in the same operations.While the conductor 115 and the light shielding film 401 may be formedthrough separate operations, the manufacturing process may be simplifiedby forming them through the same operations.

FIG. 4B illustrates a modification of the structure illustrated in FIG.4A. Description of the same components in FIG. 4B as those in FIG. 4A isomitted. In FIG. 4B, a light shielding film 403 is formed to extend froma position above the N-type semiconductor region 107 up to a positionabove the photoelectric conversion portion 801 while covering the gateelectrode 110 and the gate electrode 108. Such an arrangement mayfurther reduce incoming of light into the N-type semiconductor region106 from the side of the gate electrode 110 closer to the N-typesemiconductor region 107.

Moreover, FIGS. 4A and 4B differ from each other in inclination oflateral surfaces of the light shielding film. A lateral surface 404 ofthe light shielding film 403 in FIG. 4B is perpendicular to the surface100 of the semiconductor substrate 101, while the lateral surface 402 ofthe light shielding film 401 in FIG. 4A is inclined relative to thesurface 100. Those shapes of the lateral surface of the light shieldingfilm are optionally selectable. The shape of the lateral surface of thelight shielding film may be optionally formed by controlling thephotoresist pattern or etching conditions when the opening for the lightshielding film is formed in the insulating film 113.

The wiring structure described above in the first embodiment may also beapplied to the second embodiment. Further, the above-describedstructures may be combined with each other as appropriate. For example,the arrangement of the light shielding film in FIG. 4A may be modifiedas per illustrated in FIG. 4B.

Third Embodiment

A solid-state image pickup device according to a third embodiment willbe described below with reference to FIG. 6F. FIG. 6F is a schematicsectional view of the solid-state image pickup device, the viewcorresponding to FIG. 4A. The same components in FIG. 6F as those inFIG. 4A are denoted by the same reference numerals and description ofthose components is omitted.

FIG. 6F differs from FIG. 4A in the presence of an insulating film 601(third insulating film). An insulating film 601 is a silicon oxide film,for example. The insulating film 601 is disposed in an opening of theinsulating film 113 and is positioned between a light shielding film 602and the insulating film 113. Such an arrangement may increase insulationperformance between the light shielding film 602 and the semiconductorsubstrate 101 or between the light shielding film 602 and the gateelectrode.

A method of manufacturing the solid-state image pickup device accordingto the third embodiment will be described below with reference to FIGS.2A to 2D and 6A to 6E. The same components in FIGS. 6A to 6E as those inFIG. 6F are denoted by the same reference numerals and description ofthose components is omitted. Description of similar manufacturingoperations to those in the first embodiment (FIGS. 2A to 2G) is alsoomitted.

FIG. 6A illustrates the same structure as that illustrated in FIG. 2D.The insulating film 112 and the insulating film 202 in FIG. 2D aredenoted respectively by an insulating film 603 and an insulating film604 in FIG. 6A. The structure of FIG. 6A may be obtained through theoperations of FIGS. 2A to 2C.

Next, as illustrated in FIG. 6B, a photoresist pattern 605 is formed onthe insulating film 604. The photoresist pattern 605 serves as a maskfor use in forming a light shielding film 602 in the insulating film604. Therefore, the photoresist pattern 605 has an opening to form thelight shielding film 602. Etching is then carried out on the insulatingfilm 604 with the photoresist pattern 605 used as a mask, therebyremoving a part of the insulating film 502 and forming the contact hole504 and an opening 606 for the light shielding film 602 in theinsulating film 604. At that time, the insulating film 603 may functionas an etching stopper in the above-described etching. After forming theopening 606, the photoresist pattern 605 is removed (FIG. 6C).

Next, as illustrated in FIG. 6D, an insulating film 607 is formed tocover the insulating film 604, the conductor 115, and the insulatingfilm 603 exposed in the opening 606. The insulating film 607 is asilicon oxide film, for example. Further, the insulating film 607 isformed following respective shapes of the gate electrodes 108 and 110,lateral walls of the opening 606, etc.

A conductor film 608 serving as a light shielding film is then formedover the insulating film 607 (FIG. 6D). The conductor film 608 is, e.g.,a layered film of titanium nitride and tungsten. As in theabove-described embodiments, etching or CMP is performed on theconductor film 608 to remove an extra portion of the conductor film 608.An extra portion of the insulating film 607 disposed on the insulatingfilm 604 is further removed such that an upper surface of the conductor115 is exposed. Thus, the light shielding film 602 and the insulatingfilm 601 are formed in the opening for the light shielding film, wherebythe structure of FIG. 6F is obtained. Here, the insulating film 604becomes the insulating film 113.

In such a manner, the light shielding film 602 may be formed in theinsulating film 113 in which the conductor 115 serving as the contactplug is disposed. Further, the insulating film 601 may be formed toincrease the insulation performance for the light shielding film 602. Itis to be noted that the manufacturing method for third embodiment is notlimited to the above-described one and the manufacturing methoddescribed in the second embodiment may also be applied to the thirdembodiment. For example, the contact hole for the conductor 115 and theopening for the light shielding film 602 may be formed in the sameoperation, or in one operation.

Fourth Embodiment

A solid-state image pickup device according to a fourth embodiment willbe described below with reference to FIGS. 7A and 7B. The solid-stateimage pickup device according to the fourth embodiment is a solid-stateimage pickup device including image pickup pixels and focus detectionpixels. In comparison with the solid-state image pickup devicesaccording to the first to third embodiments, the carrier holding portionand the second transfer transistor are not included in the fourthembodiment. The same components in FIGS. 7A and 7B as those in FIG. 1A,etc. are denoted by the same reference numerals and description of thosecomponents is omitted.

FIG. 7A is a schematic sectional view illustrating the photoelectricconversion portion 801, the floating diffusion portion (FD portion) 803,and a light shielding film 701 for focus detection, which are disposedin a focus detection pixel 700. In FIG. 7A, the conductor 115 and thelight shielding film 701 having a slit 702 are disposed in an insulatingfilm 113′ that is disposed above the N-type semiconductor region 105constituting the photoelectric conversion portion 801. An insulatingfilm 301 and an insulating film 302, both being similar to those in FIG.3A and the insulating film 302 being present on the insulating film 301,are disposed over the light shielding film 701. Further, a wiring 303 bin a first wiring layer 303 and a via 304 b in a via layer 304 aredisposed in the insulating film 301. A wiring 305 b in a second wiringlayer 305 is disposed in the insulating film 302. FIG. 7B illustratesthe positional relationship among the second wiring layer 305, the lightshielding film 701, the semiconductor region 105 constituting thephotoelectric conversion portion 801, and the gate electrode 108 of thefirst transfer transistor 804 in FIG. 7A.

The slit 702 of the light shielding film 701 is offset from the centerof gravity of the photoelectric conversion portion 801. In thisembodiment, the slit 702 is arranged offset to the right in FIG. 7A.Focus detection may be performed, for example, by obtaining data withthe pixel constructed as described above and with a pixel (notillustrated) including the light shielding film that has a slit arrangedoffset to the left in FIG. 7A.

Further, the light shielding film 701 is disposed in the insulating film113′ along with the conductor 115 as in the first to third embodiments.With such an arrangement, light for the focus detection may be separatedinto two parts at a position close to the N-type semiconductor region105 constituting the photoelectric conversion portion 801, and accuracyin the focus detection may be increased. Moreover, it is possible toreduce mixing of light into the semiconductor region 107 constitutingthe FD portion 803 and to obtain higher light shielding performance.

The focus detection pixel according to this embodiment may be modifiedto have a structure including the carrier holding portion illustrated inFIG. 8.

As an application example of the solid-state image pickup deviceaccording to any of the foregoing embodiments, an image pickup systemincorporating the relevant solid-state image pickup device will bedescribed below. The image pickup system includes not only a deviceprimarily intended for photographing, such as a camera, but also adevice (such as a personal computer or a portable terminal) having thephotographing function as an auxiliary function. For example, the cameraincludes the solid-state image pickup device according to one of theforegoing embodiments, and a signal processing unit for processing asignal output from the solid-state image pickup device. The signalprocessing unit may include, e.g., a processor for processing digitaldata.

In the above description of the embodiments, the structure above thelight shielding film in the solid-state image pickup device is omitted.Above the light shielding film, a wiring structure, a protection film, acolor filter, an in-layer lens, a microlens, etc. are disposed asappropriate. Further, each of the above-described embodiments is merelyan example and may be optionally modified, and those embodiments may beoptionally combined with each other. Moreover, applications of the lightshielding film are not limited to solid-state image pickup deviceshaving the global electronic shutter function and the focus detectionfunction. The light shielding film may also be applied to solid-stateimage pickup devices having other functions, such as a function ofenlarging a dynamic range.

While the disclosure has been described with reference to exemplaryembodiments, it is to be understood that the disclosure is not limitedto the disclosed exemplary embodiments. The scope of the followingclaims is to be accorded the broadest interpretation so as to encompassall such modifications and equivalent structures and functions.

What is claimed is:
 1. A solid-state image pickup device comprising: a first transfer transistor configured to transfer carriers stored at a first semiconductor region of a first conductive type disposed in a semiconductor substrate to a second semiconductor region of the first conductive type disposed in the semiconductor substrate; a second transfer transistor configured to transfer the carriers held at the second semiconductor region to a third semiconductor region of the first conductive type disposed in the semiconductor substrate; an amplification transistor configured to output a signal based on a potential of the third semiconductor region; a first insulating film disposed over the first transfer transistor and the second transfer transistor; and a light shielding film configured to overlap an edge of a gate electrode of the first transfer resistor on a first semiconductor region side and an edge of the gate electrode on a second semiconductor region side in planar view, wherein the light shielding film has: a first bottom surface located above an upper surface of the gate electrode and below an upper surface of the first insulating film; a second bottom surface located above the first semiconductor region and at a position closer to a surface of the semiconductor substrate than the first bottom surface; and a third bottom surface located above the second semiconductor region and at the position closer to the surface of the semiconductor substrate than the first bottom surface.
 2. The solid-state image pickup device according to claim 1, further comprising a second insulating film made of a different material from that of the first insulating film, wherein the second insulating film is disposed between the second bottom surface of the light shielding film and the surface of the semiconductor substrate, and between the third bottom surface of the light shielding film and the surface of the semiconductor substrate.
 3. The solid-state image pickup device according to claim 2, wherein the second insulating film contacts with the second bottom surface of the light shielding film or the third bottom surface of the light shielding film.
 4. The solid-state image pickup device according to claim 2, wherein the second insulating film contacts with the second bottom surface of the light shielding film and the third bottom surface of the light shielding film.
 5. The solid-state image pickup device according to claim 2, wherein the second insulating film is continuously provided between the first bottom surface of the light shielding film and the surface of the semiconductor substrate, between the second bottom surface of the light shielding film and the surface of the semiconductor substrate, and between the third bottom surface of the light shielding film and the surface of the semiconductor substrate.
 6. The solid-state image pickup device according to claim 1, wherein the upper surface of the first insulating film and an upper surface of the light shielding film are substantially on a same plane.
 7. The solid-state image pickup device according to claim 2, wherein the first insulating film is a silicon oxide film, and the second insulating film is a silicon nitride film or a silicon oxynitride film.
 8. The solid-state image pickup device according to claim 2, wherein the second insulating film has a higher refractive index than that of the first insulating film.
 9. The solid-state image pickup device according to claim 1, wherein the light shielding film contains tungsten.
 10. The solid-state image pickup device according to claim 1, wherein the first insulating film is disposed over a source of the first transfer transistor.
 11. The solid-state image pickup device according to claim 1, wherein the first insulating film is disposed over a drain of the second transfer transistor.
 12. An image pickup system comprising: the solid-state image pickup device according to claim 1, and a processing unit configured to process the signal from the solid-state image pickup device.
 13. A solid-state image pickup device comprising: a first transfer transistor configured to transfer carriers stored at a first semiconductor region of a first conductive type disposed in a semiconductor substrate to a second semiconductor region of the first conductive type disposed in the semiconductor substrate; a second transfer transistor configured to transfer the carriers held at the second semiconductor region to a third semiconductor region of the first conductive type disposed in the semiconductor substrate; an amplification transistor configured to output a signal based on a potential of the third semiconductor region; a first insulating film disposed over the first transfer resistor and the second transfer transistor; a metal film configured to overlap an edge of a gate electrode of the first transfer resistor on a first semiconductor region side and an edge of the gate electrode on a second semiconductor region side in planar view, wherein the metal film has: a first bottom surface located above an upper surface of the gate electrode and below an upper surface of the first insulating film; a second bottom surface located above the first semiconductor region and at a position closer to a surface of the semiconductor substrate than the first bottom surface; and a third bottom surface located above the second semiconductor region and at the position closer to the surface of the semiconductor substrate than the first bottom surface.
 14. The solid-state image pickup device according to claim 13, wherein the metal film contains tungsten.
 15. The solid-state image pickup device according to claim 13, wherein the first insulating film is a silicon oxide film.
 16. The solid-state image pickup device according to claim 13, further comprising a second insulating film made of a different material from that of the first insulating film, wherein the second insulating film is disposed between the second bottom surface of the metal film and the surface of the semiconductor substrate, and between the third bottom surface of the metal film and the surface of the semiconductor substrate.
 17. The solid-state image pickup device according to claim 16, wherein the second insulating film is a silicon nitride film or a silicon oxynitride film.
 18. The solid-state image pickup device according to claim 16, wherein the second insulating film contacts with the second bottom surface of the metal film or the third bottom surface of the metal.
 19. The solid-state image pickup device according to claim 13, wherein the first insulating film is disposed over a source of the first transfer transistor.
 20. The solid-state image pickup device according to claim 13, wherein the first insulating film is disposed over a drain of the second transfer transistor. 